robb

import Prelude

public struct Lens<A, B> {
    private let get: A -> B
    private let set: (A, B) -> A

    public init(get: A -> B, set: (A, B) -> A) {
        self.get = get
        self.set = set
    }

JadenGeller

public struct AnyEquatable: Equatable {
	private let value: Any
	private let equals: Any -> Bool
	
	public init<E: Equatable>(_ value: E) {
		self.value = value
		self.equals = { ($0 as? E == value) ?? false }
	}
}

jochenschoellig

import UIKit


class ChatCollectionViewFlowLayout: UICollectionViewFlowLayout {
    
    private var topMostVisibleItem    =  Int.max
    private var bottomMostVisibleItem = -Int.max
    
    private var offset: CGFloat = 0.0
    private var visibleAttributes: [UICollectionViewLayoutAttributes]?

lattner

Swift Concurrency Manifesto

Author: Chris Lattner

Chinese Translation by Jason Yu

Contents

• Introduction
• Overall Vision

chriseidhof

import Foundation

protocol Channel: IteratorProtocol {
    func send(_ value: Element?)
}

/// A blocking channel for sending values.
///
/// `send` and `receive` must run in separate separate execution contexts, otherwise you get a deadlock.
final class BlockingChannel<A>: Channel {

tclementdev

libdispatch efficiency tips

The libdispatch is one of the most misused API due to the way it was presented to us when it was introduced and for many years after that, and due to the confusing documentation and API. This page is a compilation of important things to know if you're going to use this library. Many references are available at the end of this document pointing to comments from Apple's very own libdispatch maintainer (Pierre Habouzit).

My take-aways are:

• You should create very few, long-lived, well-defined queues. These queues should be seen as execution contexts in your program (gui, background work, ...) that benefit from executing in parallel. An important thing to note is that if these queues are all active at once, you will get as many threads running. In most apps, you probably do not need to create more than 3 or 4 queues.

• Go serial first, and as you find performance bottle necks, measure why, and if concurrency helps, apply with care, always validating under system pressure. Reuse

frankfka

import SwiftUI
import PlaygroundSupport


extension Double {
    func toRadians() -> Double {
        return self * Double.pi / 180
    }
    func toCGFloat() -> CGFloat {
        return CGFloat(self)